1. Field of the Invention
The invention relates to the field of bagging product units on a production line, and in particular to a method and apparatus for bagging agricultural produce pallets in preparation for modifying the atmosphere surrounding the produce inside the bag with a gas or gas mixture to retard ripening and spoilage, or to otherwise promote freshness and extend the shelf life of such produce.
2. Description of the Related Art
The ripening of agricultural produce such as tomatoes or peaches is affected by the atmosphere surrounding the produce. Many foodstuffs, such as fresh produce (e.g., strawberries, lettuce, tomatoes, cauliflower), can have their fresh condition maintained for an extended period of time by controlling the gaseous atmosphere inside the package in which they are contained. Losses during shipment and storage can be substantially decreased in this manner so that a greater percentage of fresh produce can be delivered to the consumer in acceptable condition.
Many kinds of fresh produce, a primary one being strawberries, are shipped in a quantity of boxes on a pallet base, with the entire load being enclosed by a plastic bag that is sealed to the base. U.S. Pat. No. 4,055,931, which is hereby incorporated herein by reference, discloses the providing of a special atmosphere into the containing space formed by the plastic bag by first inserting a sharp-ended ended nozzle through the plastic sheeting, evacuating the air inside the bag, and introducing gases into the interior. U.S. patent application Ser. No. 07/311,225, U.S. Pat. No. 5,046,302 filed Feb. 15, 1989, entitled "Method and Apparatus for Bagging Product Units," by Kevin J. Bolejack and Frederick Forgnone is hereby also incorporated herein by reference.
That application discloses a method and apparatus for enclosing pallets of fresh produce in sealed bags and furnishing the interiors of the sealed bags with a modified gaseous atmosphere for preserving such produce. Conventional pallets loaded with fresh produce are transported from cooling tunnels to an input conveyor. The input conveyor moves the pallets automatically one at a time to an in-line squeeze station. When a pallet is positioned at the squeeze station the conveyor stops automatically. The produce load of a pallet positioned at the squeeze station is squeezed between opposed vertical walls to suspend it above the pallet base as a downwardly movable floorplate descends to allow the pallet base to be removed and replaced with a pallet having a plastic sheet lining secured between the pallet board runners and pallet deck boards. Then the floorplate is raised to its former level to bear the weight of the loaded pallet as the produce load is unsqueezed. Next the loaded pallet with its plastic-covered base is moved by conveyor to a bagging station. The free edges of the plastic sheeting on the plastic covered base are folded upward and attached to the trays on the first tier of the produce load, and the mouth of a plastic bag is drawn downward over the top of the loaded pallet.
The bag is initially draped over an arm radiating from a bagger frame which keeps a supply of bags draped over a plurality of such radial arms at a convenient height. The arms extend from a rotatable hub so that bags can be moved into position above successive loaded pallets as they are needed. Following the bagging step the bagged pallet is moved to a turntable and sealed by rotation against spring-loaded overlapping strips of tape. After being moved, preferably automatically, to a gassing station, the sealed bag surrounding the produce is first evacuated and then filled with a suitably modified atmosphere to preserve the freshness of the produce. A preferred method for bag evacuation and subsequent gas filling in the Tectrol Atmosphere Injection System employs the insertion of nozzle means through the plastic bag. Gases inside the bag are first removed with vacuum means and then replaced with a spoilage-retardant modified gaseous atmosphere. The hole punctured in the bag by the inserted nozzle is sealed, preferably with a patch of tape. Optionally, the gassed pallet may be reoriented through 90.degree. by a repositioning turntable and sent down an inclined portion of roller-surfaced table to a pallet exit area for removal, preferably by forklift.